Bird tolerance to humans in open tropical ecosystems.

Animal tolerance towards humans can be a key factor facilitating wildlife-human coexistence, yet traits predicting its direction and magnitude across tropical animals are poorly known. Using 10,249 observations for 842 bird species inhabiting open tropical ecosystems in Africa, South America, and Australia, we find that avian tolerance towards humans was lower (i.e., escape distance was longer) in rural rather than urban populations and in populations exposed to lower human disturbance (measured as human footprint index). In addition, larger species and species with larger clutches and enhanced flight ability are less tolerant to human approaches and escape distances increase when birds were approached during the wet season compared to the dry season and from longer starting distances. Identification of key factors affecting animal tolerance towards humans across large spatial and taxonomic scales may help us to better understand and predict the patterns of species distributions in the Anthropocene.

A physiological cost to behavioural tolerance.

Few studies of animal escape behaviour simultaneously investigate behavioural and physiological responses. Differences between these response types, however, have consequences for the way in which habituation or tolerance is interpreted - behavioural habituation may incur physiological costs. We simultaneously measured heart rate (HR) and behavioural responses during standardised approaches to incubating Masked Lapwings Vanellus miles, an urban-frequenting ground-nesting bird. We describe the existence of a distinct Physiological-Initiation Distance (PID) that precedes Flight-Initiation Distance (FID) but does not necessarily precede Alert Distance (AD). Two distinct response types occurred: 'startle', where a behavioural or physiological response coincided with the appearance of a person (always the investigator; 75.9 % of 58 birds) and 'non-startle' responses, where a behavioural or physiological response occurred after the appearance of, and commencement of the approach by, the person (24.1 % or 14 birds). For birds which were not startled, the interval between the initial heart rate increase and heart rate peak increased with clutch age. For birds which were startled, longer durations of post-peak HR elevation were associated with shorter FIDs and older clutches. Thus, reduced FIDs (generally interpreted as a sign of habituation or tolerance) are associated with greater physiological costs through longer durations of elevated HR. Additionally, the existence of, often long and undetectable, PIDs suggests: 1) that behavioural measures of response underestimate responses in general, and 2) that the methodological assumption when collecting FIDs, that starting distances exceed response distances, may often be incorrect yet are visually undetectable. Further studies of a variety of taxa are warranted to determine the associations between behavioural and physiological responses, and should these associations prove reliable, they would ideally generate general predictions of PID from readily measurable behavioural metrics (FID or AD), thus enabling prescriptions to manage the consequences of human interactions with wildlife.

Correction: Social network analysis of obsidian artefacts and Maori interaction in northern Aotearoa New Zealand.

[This corrects the article DOI: 10.1371/journal.pone.0212941.].

Social network analysis of obsidian artefacts and Maori interaction in northern Aotearoa New Zealand.

Over the span of some 700 years the colonizing populations of Aotearoa New Zealand grew, with subsequent changes in levels of interaction and social affiliation. Historical accounts document that Maori society transformed from relatively autonomous village-based groups into larger territorial lineages, which later formed even larger geo-political tribal associations. These shifts have not been well-documented in the archaeological record, but social network analysis (SNA) of pXRF sourced obsidian recovered from 15 archaeological sites documents variable levels of similarity and affiliation. Three site communities and two source communities are defined based on the differential proportions of obsidian from 13 distinct sources. Distance and travel time between archaeological sites and obsidian sources were not the defining factors for obsidian source selection and community membership, rather social considerations are implicated. Some archaeological sites incorporated material from far off sources, and in some instances geographically close sites contained material from different sources and were assigned to different communities. The analytical site communities constitute relational identifications that partially correspond to categorical identities of current Maori iwi (tribal) territories and boundaries. Based on very limited temporal information, these site communities are thought to have coalesced sometime after AD 1500. By incorporating previously published and unpublished data, the SNA of obsidian artefacts defined robust network communities that reflect differential levels of Maori interaction and affiliation.

Characterisation of hyaluronic acid methylcellulose hydrogels for 3D bioprinting.

Hydrogels containing hyaluronic acid (HA) and methylcellulose (MC) have shown promising results for three dimensional (3D) bioprinting applications. However, several parameters influence the applicability bioprinting and there is scarce data in the literature characterising HAMC. We assessed eight concentrations of HAMC for printability, swelling and stability over time, rheological and structural behaviour, and viability of mesenchymal stem cells. We show that HAMC blends behave as viscous solutions at 4°C and have faster gelation times at higher temperatures, typically gelling upon reaching 37°C. We found the storage, loss and compressive moduli to be dependent on HAMC concentration and incubation time at 37°C, and show the compressive modulus to be strain-rate dependent. Swelling and stability was influenced by time, more so than pH environment. We demonstrated that mesenchymal stem cell viability was above 75% in bioprinted structures and cells remain viable for at least one week after 3D bioprinting. The mechanical properties of HAMC are highly tuneable and we show that higher concentrations of HAMC are particularly suited to cell-encapsulated 3D bioprinting applications that require scaffold structure and delivery of cells.